The preparation of siloxane-oxyalkylene or siloxane-alkyl copolymers by the hydrosilation reaction of an organohydrogen siloxane and an unsaturated olefin hydrocarbon or polyoxyalkylene is well known and reported in the literature. The hydrosilation reaction is typically performed in a low molecular weight, highly volatile hydrocarbon solvent such as benzene, toluene or xylene so as to compatibilize the reactants and aid in transfer and filtration of the copolymer products, or to moderate the exothermicity of the hydrosilation.
Less typically, the hydrosilation reaction between the organohydrogenpolysiloxane reactant and the unsaturated polyoxyalkylene or olefin reactant may be conducted without a solvent such as disclosed in U.S. Pat. No. 3,980,688 or conducted in an oxygen containing solvent such as an ether, a polyether, or a lower or higher molecular weight alcohol.
For instance, U.S. Pat. Nos. 3,280,160 and 3,402,192 disclose the preparation of copolymers in n-butyl ether and in a 50/50 mixture of isopropyl alcohol/toluene, respectively. Also in U.S. Pat. No. 4,122,029 the use of isopropyl alcohol is disclosed and U.S. Pat. No. 3,518,288 teaches the use of n-propanol/toluene as a suitable solvent for the preparation of siloxane-oxyalkylene copolymers. U.S. Pat. No. 4,857,583 discloses the use of high boiling point polar polyols as a reaction solvent wherein the solvent is not removed from the final product following the preparation of the siloxane-oxyalkylene copolymers. U.S. Pat. No. 5,153,293 teaches the use of monocarboxylate esters of alkanediols, limited to 2,2,4-trimethyl-1,3 pentanediol monoisobutyrate, as the reaction solvent. While this is a good reaction solvent, it has been found to contribute to glass fogging when utilized in the manufacture of polyurethane foam for automotive interiors. The term "glass fogging" used herein refers to the phenomenon of volatilization of product(s) from e.g. a polyurethane foam when exposed to heat and the redeposition of the volatilized product(s) onto another surface such as the interior of automotive windows.
In the majority of the aforementioned processes, the hydrocarbon solvent is removed after the hydrosilation reaction is completed, since in most cases, the solvent is too flammable, toxic or otherwise detrimental to the final product or further processing steps in which the copolymer is utilized. This is particularly true of volatile aromatic or hydrocarbon solvents if the final product enters into personal care applications where human contact with the final product is expected, or in urethane foam applications where potential "glass fogging" can occur in interior automotive foam applications. Thus, in the processes disclosed in most of the above patents, the solvent was removed from the reaction product after completion of the hydrosilation reaction. Removal of said solvents increases batch cycle times and necessitates disposal of the solvent in an environmentally safe manner such as incineration. Of the above mentioned solvents, isopropyl alcohol (IPA) and toluene are most commonly used. Toluene and IPA are known to compatibilize or improve the miscibility of the siloxane and the unsaturated polyoxyalkylene(s) so that the reaction proceeds more readily. However, disadvantages attend their use. Such disadvantages include: (A) IPA competes with the unsaturated polyether for the silanic sites (SiH) on the siloxane backbone resulting in the formation of the isopropoxysilyl, (CH.sub.3).sub.2 CHOSi, functional group which reduces surfactant performance in urethane foam; (B) IPA reacts with isocyanate in polyurethane foam formulations effectively lowering the isocyanate index of the formulation, so that the IPA must be stripped from the product and recovered, a process which is both time consuming and expensive; (C) IPA is miscible with water which is harmful in the manufacture of polyurethane foam surfactants; and (D) toluene and IPA are flammable which creates additional manufacturing problems. In addition, prolonged stripping of surfactants manufactured with toluene or IPA can lead to degradation of surfactant performance.
A few instances have been reported in the literature where for one reason or another it was neither necessary nor desirable to separate the copolymer from the reaction solvent. For example, U.S. Pat. No. 4,520,160 discloses the use of saturated higher alcohols, such as isostearyl alcohol, as a reaction solvent which purposely need not be removed from the resulting copolymer when it is used subsequently in personal care compositions as emulsifiers. U.S. Pat. Nos. 4,857,583 and 5,153,293 also teach that higher boiling point polyols or monocarboxylate esters of an alkanediol, respectively, purposely need not be removed from the resulting copolymer when it is used subsequently in urethane foam formulations. However, as disclosed in these patents, the potential exists for the hydroxy functionality of the solvents to compete with the unsaturated polyoxyalkylene for SiH sites on the siloxane backbone. Additionally, these alcohols contain volatile species which produce "glass fogging" when employed in the manufacture of automobile interior trim foam.
In many instances, however, the solvent does not enter into any further reactions but remains in the final product as is, and hence, there is no need for its removal if it does not adversely affect the production process or the product's intended use in personal care, urethane foam or coatings applications. Thus in some cases, such as personal care products of U.S. Pat. No. 4,520,160, it may even be beneficial to have some of the solvent present in the final product. However, if the copolymer is to undergo further reactions before preparation of the final end-use product is complete, presence of the solvent might adversely affect such reactions and hence its removal after the hydrosilation reaction is desired. For example, if one uses copolymers containing monohydric alcohols in urethane foam applications, these alcohols will enter into the urethane reaction and act as reaction chain terminators in a detrimental fashion because they contain only one hydroxy group. Also as previously indicated, some solvents may be toxic or not suitable for human contact or otherwise undesirable in further processing of the copolymer.
It is therefore an object of the present invention to provide an improved process for the preparation of siloxane-oxyalkylene and siloxane-alkyl copolymers. Another object of the invention is to provide a process for the preparation of lower volatility, clear, homogeneous siloxane-oxyalkylene copolymers or alkyl-siloxanes that are useful and beneficial in the formulation of urethane foam products and wherein it is not necessary to remove the reaction solvent. A further object of the invention is to provide an improved process for the preparation of clear, homogeneous siloxane-oxyalkylene or alkyl-siloxane copolymers which are either prepared in natural vegetable oil or are mixed with natural vegetable oil to arrive at surfactant blends that when utilized in polyurethane foam, cause the foam to have improved compression sets, reduced flammability and reduced fogging tendencies, and other desirable features. These and other objects will readily become apparent to those skilled in the art in the light of the teachings contained herein.